Tholian E&F2 infopage
The Tholians are not native to our galaxy, but migrated here from another. They are the survivors of a race that once dominated their native galaxy, the exact location of which is unknown. The subject races of the former Tholian Empire rose in a galaxy-wide revolt some 200 years ago, overthrowing the Tholian dictators. The Tholians of our galaxy are the descendants of a group that escaped the debacle and managed, by means yet unknown, to bring their planet (which was a provincial capital and a small Dyson sphere) with them.
Tholians are crystalline creatures who exist in very high temperatures. It can be assumed that boarding party actions employ special environmental suits for one or both sides.
They settled on the edge of our galaxy at the end of the spiral arm that includes the Klingon homeworld. The Klingons had claimed this territory (and the Federation had tacitly accepted the claim), but the Klingons had not colonized it extensively. The Tholians now claim it as their own and defend it fiercely, which explains the considerable hatred between them and the Klingons. The Federation has turned a deaf ear to Klingon requests, through diplomatic channels, for repatriation of the colonists and base crews from the area. It is doubtful that any survived the Tholian arrival.
Klingons could probably crush the Tholian Holdfast at will, but have been
unable to spare enough ships to do so without dangerously weakening their
other frontiers. Also, the Federation has announced that it will not
tolerate aggression against the Tholians. This would presumably involve
Federation fleets operating in neutral or Klingon territory since foreign
forces are not welcome inside the Holdfast. The Tholians have denounced
Federation assistance and declared strict neutrality, but are fully aware
that their survival in a crisis would depend on Federation assistance. The
Tholians are masters of playing off one side against the other; the first
principle of war taught in their academy is "Let's you and him
(from the Tholian will page)